1. Field of the Invention
The present invention relates to means for closing openings in hatches, tanks, or other containers. In some applications it is desired to close such an opening while maintaining access by means of a temporarily installed pipe or other obstruction extending through the opening. This invention is concerned with closures not only for unobstructed openings, but for openings that must receive such obstructions as well.
2. Description of the Prior Art
Closures which operate in a rotary or twisting manner are well-known. The familiar snap camera usually operates in this manner to adjust the amount of light admitted, for example. Other "iris"-type closures are described in the following patents: U.S. Pat. No. 1,992,225 to Wickersham et al. issued Aug. 15, 1933, U.S. Pat. No. 1,999,699 to Koch issued Apr. 30, 1935, U.S. Pat. No. 2,037,663 to Lalor issued Apr. 14, 1936, U.S. Pat. No. 2,307,273 to Hughes issued Jan. 5, 1943, U.S. Pat. No. 2,649,272 to Barbato issued Aug. 18, 1953, U.S. Pat. No. 3,101,736 Egger issued Aug. 27, 1963, U.S. Pat. No. 3,159,179 to DeLain issued Dec. 1, 1964, U.S. Pat. No. 3,329,396 to Heaton et al issued July 4, 1967, and U.S. Pat No. 3,787,022 to Wilcox issued Jan. 22, 1974. These prior art devices, however, all require the use of hinged plates which slide or swing in and out of a central opening. These cams or plates must be geared mechanically to progressively shut or open a main opening. As such, they suffer the drawbacks of all mechanical devices utilizing a multiplicity of moving parts. furthermore, While, in some cases, they are adapted to closing about an abstruction placed in the opening, the obstruction must be precisely located in the center of the opening to avoid an improper seal about the obstruction. It is, therefore, desirable to produce a closing device of uncomplicated operation requiring a minimum of moving parts and that is adaptable to closing about an obstruction which may not be precisely centrally located within the opening.